Production of shale oil

ABSTRACT

Process for recovering shale oil from oil shale by retorting with synthesis gas, i.e., a mixture of carbon monoxide and hydrogen, generated by partial combustion of byproduct gas with oxygen, wherein part of the heat required for retorting is provided by the hot synthesis gas, and additional hydrogen is produced in the oil shale retort by the water-gas shift reaction, the shale acting as a catalyst; and the process being selfsufficient in requiring no external source of water.

United States Patent [72] Inventors Warren G. Schlinger 3,051,644 8/1962Friedman et al 208/1 1 Pasadena; 3,074,877 1/1963 Friedman et al...208/1 1 Dale R. Jesse, Hacienda; Joseph P. 3,480,082 1 1/1969 Gillilandet al. 208/1 1 X Tammy whmkr Cull Primary Examiner-Curtis R. Davis [21]Appl. No. 889,449 [22] Filed Dec. 31 1969 Attorneys-Thomas I-I. Whaleyand Carl 0. RIes [45] Patented Nov. 2, 1971 [73] Assignee Texaco Inc.

New York, N.Y.

[541 PRODUCTION OF SHALE OIL 7 Chins, 1 m, m ABSTRACT: Process forrecovering shale 011 from oil shale by retorting with synthesis gas, re,a mixture of carbon monox- [52] U.S. Cl 208111 w and hydrogen generatedby partial combustion f [5 It. a e byp du t g oxygcn wherein pan of theheat required [50] Field 01 Search 208/11 for "toning is provided by thehot synthcsis gas and d tional hydrogen is produced in the oil shaleretort by the [56] Rem-um water-gas shift reaction, the shale acting asa catalyst; and the UNITED STATES PATENTS process being self-sufficientin requiring no external source of 3,044,948 7/1962 Eastman et al.208/ll water.

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nZm/Jh/e #20 a fizv' 'yn/Jeszls 605 M/er 1 PRODUCTION OF SHALE OILBACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to aprocess for the recovery of oil from oil shale. In one ofits more specific aspects, it relates to an improved process ofhydrotorting oil shale with carbon monoxide and hydrogen generated bypartial oxidation of gaseous byproducts to produce shale oil of improvedquality and yield.

2. Description of the Prior Art Oil shale consists of compactedsedimentary inorganic rock particles, generally laminated and partly orentirely encased with a high molecular weight organic solid materialcalled kerogen, which is present in the amount of about6 to 22 wt.percent.

Crude shale oil may be obtained by pyrolysis of raw oil shale. Thus, rawshale may be subjected to destructive distillation in a retort at atemperature of about 850 to 950 F. The chemical decomposition of thekerogen which takes place by the action of heat along yields crude shaleoil vapors, together with water, gas, and spent shale containing acarbonaceous residue and mineral matter.

The application of hydrogen to the retorting of oil shale, for exampleby the processesof U.S. Pat. No. 3,117,072 and ,U.S. Pat. No. 3,224,954issued to DuBois Eastman and WarrenC. Schlinger, gives increased yieldsof shale oil of improved quality. Oil shales usually occur in desertareas where the lack of process water has traditionally been consideredadrawback to development of the oil shale deposits for recovery of shaleoil.

SUMMARY We have devised a continuous process for retorting raw oilshale, thereby obtaining near maximum yields of shale oil of reducednitrogen and sulfur content, as compared with the Fischer Assay. In oursystem, a synthesis gas generator produces a mixed stream comprisinghydrogen and carbon monoxide at a temperature in the range of aboutl,700-3,000 F. by the partial oxidation of recycled byproduct gasesfromthe process. At a temperature in the range of about 750 to 1,500 F. anda pressure in the range of about 100 to 20,000 p.s.i.g. the raw oilshale in a shale retort zone is then contacted by the effluent gasstream from the reaction zone of the synthesis gas generator, therebysupplying hydrogen and some of the heat for hydrotorting the raw oilshale. Further, watergas shift reaction occurs simultaneously with thehydrotorting in the shale retorting zone. In such instance, spentshaleserves as a shift catalyst so that some of the CO in the synthesis gasis converted into H Thus, a gaseous mixture comprising hydrogenatedshale oil vapors, H 0, anduncondensed l-l carbon oxide gases is producedby the process. All or a portion of the uncondensed gases may be thenintroduced into a gaspurifying zone, where byproduct fuel gas is removedand is recycled to the gas generator as feed, alongwith the unpurifiedportion of said uncondensed gases and optionally with a minor amount ofmakeup fuel gas from an external source. Addition of 11,0 to the gasgenerator or to the shale retort zone or both is optional. However, noexternal source of water is required as sufficient H is produced by theprocess to fulfill any process requirements.

THe principal object of this invention is to provide an improved processfor recovery of shale oil from oil shale.

Another object of this invention is to provide a process for pyrolyzingand hydrogenating raw oil shale to produce an upgraded shale oil,utilizing hot synthesis gas to provide heat and hydrogen for theprocess.

Still another object is to provide a process which is selfsustainingwith respect to process water requirements, wherein fuel gases producedin the system are reacted with oxygen in the absence of H,O in asynthesis gas generator to produce hot process gas for recovery of shaleoil from oil shale.

A still further object of this invention is to provide a process forsimultaneously retorting oil shale and hydrogenating the shale oil vaporreleased to produce increased yields of a shale oil with a substantiallyreduced nitrogen and sulfur content.

The accompanying FIGURE illustrates diagrammatically process steps inthe method of this invention.

DESCRIPTION OF THE INVENTION The present invention pertains to animproved hydrotorting process in which synthesis gas i.e., gaseousmixture comprising H, and COis used to recover high qualityshale oilfrom raw oil shale at greater yields than the Fischer Assay.

The synthesis gas is produced by the partial oxidation of gaseousbyproducts from the subject process in a separate conventionalnoncatalytic free-flow synthesis gas generator. A suitable gas generatorfor use in the process is described in US. Pat. No. 2,582,938 issued toDuBois Eastman. The synthesis gas is produced in the gas generator at apressure in the range of about 100 to 3,500 p.s.i.g. and atemperature inthe range of about l.700 to 3,000 F.

Feed gas to the synthesis gas generator consists of a gaseous mixturesubstantially comprising the combustible gaseous byproducts from thesubject process, optionally with a relatively minor quantity ofsupplemental makeup fuel gas from an external source. The feedgasmixture comprises mostly CO, H and CO, and relatively smaller amounts ofCH, and

H S. Preferably, the gaseous feed is introduced into the gas generatorat a temperature in the range of 300 to 750 F. It is optional to providewater as part of the feed to the generator.

The oxidizing gas which is fed to the synthesis gas generator,preferably at a temperaturein the range of 250 to 350 F., may beselected from the group consisting of substantially pure oxygen (greaterthan 95 mole percent 0 and oxygenenriched air (greater than 21 molepercent of O Suitably, sufficient free oxygen is introduced into thereaction zone so that the ratio of atoms of oxygen to atoms of carbontherein is in the rangeofabout 0.08to 1.5.

Raw oil shale in the shale retort zone is then contacted with theaforesaid synthesis gas at a temperature in the range of about 750=tol500 F.,,and preferably below 1,000 F. for example 800 to 950 F., at apressure in the range of about 100 to 20,000 p.s.i.g. Preferably, tosave on gas compressioncosts, the pressure in the synthesis gasgeneratorand the shale retort zone are substantially the same, lessordinary pressure drop in the lines. Sufficient synthesis gas issupplied to the shale retort zone to provide a H +CO consumption in therange of about 1,000 to 20,000, and preferably about 1,300 s.c.f. of H+CO per ton of oil shale treated.

The oil shale may be in a dry form when treated or slurried with aliquid hydrocarbon fuel e.g., shale oil, crude oil. The shale retortzone may constitute a fixed or fluidized bed of raw oil shale particles,as described for example in US. Pat. No. 3,224,954 issued to Warren G.Schlinger and DuBois Eastman; a tubular retort, as more fully describedin the aforementioned U.S. Pat. No. 3,117,072; or a fracturedsubterranean oil shale stratum as described for example in US. Pat. No.3,084,919 issued to William 1.. Slater, thereby effecting pyrolysis andhydrogenation in situ. A particular advantageous method for retortingthe raw oil shale is described in our coassigned copending applicationSer. No. 786,951. Further, the oil shale retort zone may be externallyheated; or substantially all or partof the heat required for retortingmay be supplied by the synthesis gas.

Optionally, the raw oil shale is contacted with H 0 in the shale retortzone at the same time that the shale is contacted with hot synthesisgas. The H O, either in the form of supplemental liquid water or steam,may be introduced into the shale retort zone along with the synthesisgas, or the H 0 may be separately introduced. introducing supplemental HO into the oil shale retort zone was found tohave several new andunobvious results, making it a preferred mode of operation. It wasunexpectedly found that when oil shale is contacted with H,O

in the shale retort zone, the endothermic decomposition of inorganiccarbonates in the production of CO, is repressed. This saves hydrogen,as CO, would ordinarily react with H, to form H,O and CO. Thus by H,Oaddition, there is a savings of energy in the form of heat ordinarilyconsumed by the decomposition of inorganic carbonates; and further,there is a considerable reduction of hydrogen consumption. Also, themass velocity of the gas mixture through the shale retort zone, and theheat transfer coefficient of the mixture are increased by the additionof H O. in addition, vaporization and expansion of water in the oilshale tends to disintegrate the shale particles and facilitate theatomization of the shale oil. Also, coking of the shale may be minimizedor eliminated at a substantially reduced hydrogen consumption.

Unobvious advantages for introducing H,O underpressure into the oilshale during hydrotorting of shale slurries in a tubular retort include:(1 l greater concentrations of shale may be incorporated in pumpableoil-shale slurries, and (2 clogging of the retort tubing is prevented.Thus, a portion of the water produced by our process, at a suitabletemperature in the range of about 100 to 500 F. is preferably recycledto and introduced into the shale retort zone in an amount of about 0.01to 0.6 ton of H,0 per ton of raw oil shale, and preferably about 0.1 to0.4 ton of H per ton of raw oil shale. Both the synthesis gas and thesupplemental H 0 may be supplied to the oil shale retort zone, forexample, at a pressure of about 25 to 200 p.s.i.g. greater than thesystem line pressure.

In one embodiment of our invention a portion of the H 0 produced by theprocess may be used to cool the hot effluent gas from the synthesis gasgenerator from a temperature of about 2,200 F. to about 1,000 F. byrecycling byproduct H O to a synthesis gas quench zone and quenching theeffluent synthesis gas from the gas generator in the manner shown inU.S. Pat. No. 3,232,728 issued to Blake Reynolds. One advantage of thisembodiment of the invention is that all of the water required in theshale retorting step may be picked up by the synthesis gas vaporizingthe quench water during cooling.

It was unexpectedly found that spent shale in the shale reac tion zoneacts like a shift catalyst, and that simultaneously with thehydrotorting in the oil shale reaction zone the CO supplied by thesynthesis gas undergoes an exothermic watergas shift reaction to produceadditional hydrogen gas and CO Thus the following additional savings arebrought about by our improved process: (1 costly pure hydrogen may bereplaced by relatively inexpensive synthesis gas containing H to effectdenitrogenation and desulfurization of shale oil, (2 additional H, isproduced by the water-gas shift reaction from C0 supplied by low costsynthesis gas, and (3 additional heat is released in the tubular retortduring the water-gas shift reaction.

The residence time in the oil shale retort zone must be long enough topermit pyrolysis and disintegration of the raw oil shale andhydrogenation of the shale oil vapors. However, excess time in the shaleretort zone may cause coking and result in degraded shale oil. Thus atthe previously mentioned conditions, the preferred residence time isfrom about 20 minutes to 5 hours and generally about 30 minutes in abatch retort or a fixed bed of shale at a pressure in the range of about1,000 to 2,500 p.s.i.g. Further, the residence time is preferablymaintained at about-one-fourth to 5 minutes in a tubular reactor at apressure in the range of about 100 to 20,000 p.s.i.g. and preferably inthe range of 300 to 1,000 p.s.i.g.

The gaseous effluent stream leaving the reaction zone comprises vaporsof shale oil and water, unreacted hydrogen, NH CO, CH, H S, C0,, and maycontain a small amount of entrained spent shale particles (about 250 to350 mesh). When necessary, the entrained spent shale particles may beseparated from the remaining gaseous stream by means of a conventionalgas-solids separator, or for example a chamber with a downwardlyconverging bottom equipped with baffling elements. The hot gaseouseffluent leaving overhead from the reaction zone or the gas-solidsseparator is cooled below the dewpoints of the water and the shale oil.In a gas-liquids separator the shale oil and water are separated bygravity from each other and from the uncondensed gases.

Depending on the composition of the synthesis gas to the oil shalereaction zone, the uncondensed gases withdrawn from the top of thegas-liquids separator having the following approximate composition inmole percent dry basis: H, 45 to 85, H 5 0 to 2.0, CO, 1.0 to 15.0, NH,0.05 to 0.50, CO 3.0 to 30.0, and CH, 2.0 to 20.0. This gas may becompressed and recycled to the synthesis gas generator either alone orin combination with makeup fuel gas. However, to prevent the buildup ofimpurities all or a portion of this gas stream may be first divertedinto 'a gas purifier. A suitable gas purifier of conventional typeutilizing refrigeration and chemical absorption to effect separation ofthe gases, such as described in U.S. Pat. No. 3,001,373 issued to DuBoisEastman and Warren G. Schlinger may be used. A purified gaseous mixture,essentially comprising H and CO with a minor amount of CH,, is withdrawnfrom the gas purifier and recycled as feed to the synthesis gasgenerator.

In conclusion, by the process of our invention, oil shale is treatedwith a hot hydrogen-rich gas, i.e., synthesis gas, and preferably H 0.As previously described, the following occurs: l kerogen in oil shale israised to a high enough temperature to fracture, (2 pyrolysis of thekerogen and hydrogenation of the shale oil produced, (3 the porousstructure of the shale is maintained during retorting to enable crackedkerogen in the interior to quickly escape before being converted topolymeric or gaseous products, and (4 rapid disintegration of raw oilshale into minute particles free of carbonaceous matter. ln our process,shale oil, H 0, and synthesis gas act as heat transfer agents byconducting heat to the surface of the shale particles. The H,O alsoreduces the hydrogen consumption and heat load for a given yield ofshale oil. The hyd ogen is able to permeate into shale matrix so that itis available to properly terminate the hydrocarbon fractures before cokeis formed plugging the pathway to the surface of the shale particle. Bythe process of our invention, the higher boiling hydrocarbons aresubjected to viscosity breaking with substantially immediatehydrogenation of the molecular fragments and without further breakdown,thereby materially increasing the production of material boiling in the400-700 F. range without substantially increasing the lower boilinggasoline range materials or forming normally gaseous hydrocarbons andheavy tars and coke. Thus, the formation of heavy polymers, unsaturatedhydrocarbons and carbonaceous residues, which characterize knownprocesses, are suppressed.

Evidence of the success of this method can be seen by the unusually highyield of high quality product shale oil, the production of sufficientwater to satisfy the needs of the process, and by the finely groundkerogen-free quality of the spent shale. For example, shale oil yieldsof about 34.0 gallons and more per ton of raw shale may be produced bythe subject process in comparison with Fischer Assay shale oil of about31.0 gallons per ton. This represents a minimum increase in yield ofabout 10 percent and marks an improvement over the yield fromcontemporary processes. Also, examination of the hydrotorted shale oilproduced shows it to be of superior quality; that is, compared withFischer Assay shale oil from the same shale, the sulfur and nitrogencontent are each about 25 to 35 percent lower. Finally, theself-sustaining features of the process makes it particularly attractivefor use in arid lands.

EXAMPLE OF THE PREFERRED EMBODIMENT The following example is offered asa better understanding of the present invention but the invention is notto be construed as limited thereto.

ln run 1, chunks of Colorado Oil Shale having a maximum cross-sectionaldimension of about 4 inches and having a Fischer Assay of about 31.2gallons of shale oil per ton of raw oil shale and 2.9 gallons of H 0 perton of raw oil shale are charged into a fixed bed vertical oil shaleretort 1 foot in diameter by 40 feet long. The retort is charged hourlywith 2,000 pounds of oil shale per batch. The system is purged of airand 10,170 s.c.f.h. of synthesis gas, to be further described, at atemperature of about 950 F., and 30 gallons per hour of supplemental H Oat a temperature of 900 F. are passed through the oil shale retort zonemaintained at a pressure of about 500 p.s.i.g. The gaseous effluentstream leaving from the top of the oil shale retort comprisesessentially vaporized hydrogenated lterogen products, e.g., shale oil,and water, as well as such gases as CO,, H CO, H 5, N11 and CH,. Thegaseous effluent stream is then cooled below the dewpoint of the productshale oil and the water, which are thereby liquefied and separated bygravity in a gas-liquids separator from each other and from anuncondensed gaseous mixture. To prevent the build-up in the system ofgaseous impurities, the uncondensed gas mixture is introduced into aconventional gas purifier.

A continuous stream of about 938 s.c.f.h. of noncombustible off-gas fromthe gas purifier is discharged from the system, while the remainingpurified gas is introduced into the top of the synthesis gas generator.This fuel gas mixture comprises in mole percent dry Basis: H 573, CO38.2, CO, 0.0, Cl-l 3.5, H 8 0.0, and N 1.0. Further, about 550 s.c.f.h.of makeup gas from an external source having the following compositionis also fed to the synthesis gas generator: CH, 95.1, C, H 2.0, and CO,2.9.

About 71 lbs/hr. of 95+ mole percent of oxygen at a temperature of about300 F. are fed to the reaction zone of the synthesis gas generator. inthis example, the synthesis gas generator operates without the additionof supplemental H O. About 10,170 s.c.f.h. of synthesis gas is producedin the reaction zone of the generator at a temperature of about 2,200 F.and a pressure of about 550 p.s.i.g. The synthesis gas has the followingcomposition (mole percent dry basis): H, 58.5, C 38.2, CO, 2.4, N, 0.8and Ch, 0.1. The synthesis gas is cooled in a waste heat boiler to atemperature of about 950 F. and is introduced into the shale retortzone, as previously mentioned.

For comparative purposes, run 2 was made under the same conditions asrun 1 but with no supplemental H O being introduced into the shaleretort zone.

A summary of the operating conditions and the products recovered forruns 1 and 2 are shown in table 1 along with, for comparison, shale oilproduced by the Fischer Assay.

TABLE I Run Run Fischer Operating conditions assay Synthesis gasreaction zone:

Pressure, p.s.l.g 550 550 N Tempemture, F 2, 200 2, 200 N Fuel gasmixture, S.c.F.h 8,567 7,475 N Make-up gas, S.c.F.h 550 862 N Shaleretort zone:

Pressure, p.s.i.g 500 500 N Temperature, F 950 950 N Retorting period,hrs. 1 1 N Synthesis gas s.c.f. 10,170 10, 170 N Supplemental H20,lbs/hr 30 None N Consumption of hydrogen (from syn.

gas), s.c.f./barrel of shale oil produced. 1, 590 2, 470 N Recovery,product shale oil:

Gals/ton of raw shale 34. 3 33. 31. 2 Percent Fischer assay... 110 107.4 100. 0 Gravity, API 24. 0 24. 5 24. 1 Viscosity SSU at 122 F 55 4950.0 Pour point, F 70 65 75 Sulfur, Wt. percent- 0. 65 0. 65 0. 98Nitrogen, wt. ercent 1. 65 1. 65 1. 80 Conradson car on, wt. percent 4.50 4. 28 2. 3 Characterization factor (K) 11. 5 11.5 11. 4AS'lIiPdistillation, F.:

NOTE.-N =Not applicable.

By a comparison of the results in table 1, it may be shown that in run 1with supplemental H O being introduced into the shale reaction zone theconsumption of hydrogen (as supplied by the synthesis gas) is less thanin run 2 where no H O is added. However, the water yield for run 1 isless than that for run 2. This supports the theory that water injectioninto the shale retort inhibits the undesirable decomposition of shalecarbonate, which reaction absorbs heat and liberates CO that reacts withhydrogen to form water.

The results clearly show that compared with the Fischer Assay (column 3superior yields of product shale oil are obtained from runs 1 and 2 andthe quality of the shale oil is improved. Further, adding supplemental HO to the shale retort zone, as in run 1, is preferred.

The process of the invention has been described generally and byexamples with reference to oil shale and gas mixtures of particularcompositions for purposes of clarity and illustration only. It will beapparent to those skilled in the art from the foregoing that variousmodifications of the process and materials disclosed herein can be madewithout departure from the spirit of the invention.

We claim:

1. A process for hydrotorting raw oil shale to produce shale oil whichcomprises: generating synthesis gas comprising CO and H by the partialoxidation of byproduct gas from the subject shale hydrotorting processas defined hereinafter; contacting raw oil shale with said synthesis gasin a shale retorting zone at a temperature in the range of about 750 to1,500 F. and for a sufficient time to pyrolyze said oil shale therebyproducing a vaporous effluent stream comprising denitrogenated anddesulfurized shale oil vapor, H 0, 11,, C0, C0 and CH. introducing saidvaporous effluent stream into a separating zone; separately withdrawingfrom said separating zone hydrogenated shale oil and uncondensed fuelgases; and supplying at least a portion of said uncondensed fuel gasesto said synthesis gas generator as feed.

2. The process of claim 1 with the added steps of introducing H O intosaid shale retorting zone and withdrawing water from said separatingzone.

3. The process of claim 2 wherein said H,0 is introduced in the amountof about 0.01 to 0.6 tons of 11,0 per ton of raw oil shale treated.

4. The process of claim 1 wherein sufi'icient synthesis gas isintroduced into said shale retorting zone to provide 1,000 to 20,000s.c.f. of H +CO per ton of raw oil shale treated.

5. The process of claim 1 wherein said synthesis gas is generated at apressure substantially equivalent to the pressure in said shaleretorting zone and is introduced into said shale retorting zone and isintroduced into said shale retorting zone at a temperature in the rangeof about 800 to about 1,000 F. and at a pressure in the range of about300 to 1,000 p.s.i.g.

6. The process of claim 1 wherein said shale retorting zone comprises atubular retort, and said raw oil shale is pulverized and slurried withshale oil.

7. The process of claim 1 with the added step of cooling said synthesisgas in a quench zone with water obtained from said separating zone.

Patent No.

Inventor(s) W. Schlinger,

Dated November 2 1971 Dale Jesse 8c J. Tassoney It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

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2. The process of clAim 1 with the added steps of introducing H2O intosaid shale retorting zone and withdrawing water from said separatingzone.
 3. The process of claim 2 wherein said H2O is introduced in theamount of about 0.01 to 0.6 tons of H2O per ton of raw oil shaletreated.
 4. The process of claim 1 wherein sufficient synthesis gas isintroduced into said shale retorting zone to provide 1,000 to 20, 000s.c.f. of H2+CO per ton of raw oil shale treated.
 5. The process ofclaim 1 wherein said synthesis gas is generated at a pressuresubstantially equivalent to the pressure in said shale retorting zoneand is introduced into said shale retorting zone and is introduced intosaid shale retorting zone at a temperature in the range of about 800* toabout 1,000* F. and at a pressure in the range of about 300 to 1,000p.s.i.g.
 6. The process of claim 1 wherein said shale retorting zonecomprises a tubular retort, and said raw oil shale is pulverized andslurried with shale oil.
 7. The process of claim 1 with the added stepof cooling said synthesis gas in a quench zone with water obtained fromsaid separating zone.